After reviewing over 150 patents from the class 320.109, class 439.10 and class 439.34, it is deemed that this invention is unique and new over the prior art.
The problem of transferring electrical energy to moving vehicles has received substantial attention in the transportation and material handling community. Consequently there is a rich array of technologies available in the prior art. The prior art can be broadly classified into following categories:
Cable with connectors or pedals: (U.S. Pat. No. 6,185,501) All such systems involve manual connection and disconnection of vehicle to the infrastructure. Apart from the fact that these systems do not offer automation, they do have safety issues arising from a potentially complex tangle of wires to be managed as well as possibilities of accidental drive off by a forgetful driver while the vehicle is still tethered to charging outlet.
Large scale inductive transfer: (U.S. Pat. No. 5,573,090). These systems involve oversized primary induction coils embedded under parking spot. Large dimensions are intended to cover the vehicle parking misalignments. Such systems suffer from the excessive inductive energy wastage and involve complex infrastructure modifications that are unsuitable for modern personal use vehicles.
Overhead pantographs: (RE29,994, U.S. Pat. No. 3,955,657, U.S. Pat. No. 5,651,434) All such systems are bulky intrusive configurations that need involved installation and maintenance of overhead bus bars. These systems also involve single energy transfer channel due to the cross bars with single conductors. The second connectivity channel is taken from underground connection. This leaves no room for additional channels for energy transfer interlocks, which are crucial from the operational safety viewpoint.
Electromagnetic radiation coupling: (U.S. Pat. No. 7,068,991, U.S. Pat. No. 6,792,259, U.S. Pat. No. 6,114,834, U.S. Pat. No. 5,982,139) A handful of patents refer to a narrow radiation beam emanating from an infrastructure device and hitting energy receiving devices on the roof of vehicles. Such systems still need a fair amount of manual alignment, but most importantly have very limited energy transfer rates for a safe level of radiation.
Conical/compliant receptacles: (U.S. Pat. No. 7,023,177, U.S. Pat. No. 6,614,204, U.S. Pat. No. 5,850,135, U.S. Pat. No. 5,696,367, U.S. Pat. No. 5,498,948, U.S. Pat. No. 5,272,431) These systems offer a limited tolerance to vehicle to parking stall misalignments. The operator is still expected to home into the receiving or compliant zone of the receptacle and stop just in time not to push against the infrastructure. In addition to expecting specific behavior from drivers, an accidental poor alignments as well as fast approach pose collision threat and will degraded the operation and reliability of such systems.
Active location seeking robotic arms/trolleys: (U.S. Pat. No. 6,859,010, U.S. Pat. No. 5,821,731, U.S. Pat. No. 5,703,461, U.S. Pat. No. 5,696,367, U.S. Pat. No. 5,654,621, U.S. Pat. No. 5,646,500, U.S. Pat. No. 5,617,003, U.S. Pat. No. 5,461,298, U.S. Pat. No. 5,272,431) There are many variants of these systems depending on the sensing scheme used as well as actuation schemes used. Such systems are relatively complex and depend on reliability of several sensors and motion control loops. A miss-calibrated/drifted system could pose a spectrum of problems ranging from scratching the shiny paint of vehicle to simply not being able to connect the vehicle. Apart from the intrusive nature of the robotic arms, both the trolleys as well as robotic systems are susceptible to vandalism in open infrastructure applications.
Physical and virtual guiding systems for homing: (U.S. Pat. No. 6,525,510, U.S. Pat. No. 5,850,135, U.S. Pat. No. 5,461,298, U.S. Pat. No. 5,341,083, U.S. Pat. No. 4,496,896) The first category of these systems either employ mechanical guides for vehicle tires, forcing the vehicle to a relatively precise location for the automatic connector to mate with now precisely located vehicle side counterpart. Some other systems involve passive guidance to the drives, either based on a sensor pair, a dashboard or infrastructure based display device or through grid markings on the pavement. Such systems are either large footprint and tend to be bulky, or are imprecise (passive guidance) and need further connectivity assistance from conical, compliant or active search components.
Contactor arrays: Such systems have multiple connectors placed on infrastructure that will end up connecting with relatively few contactors on the vehicle side and vice versa. The vehicle to parking stall misalignment is compensated by multiple conductors. This patent generally falls in this category of devices. Specifically: U.S. Pat. No. 6,307,347 describes a pair of two dimensional grids, each grid being permanently dedicated for one channel of connectivity. This not only increases the number of connectors (proportional to l2) per channel of connectivity, but also needs each grid big enough to tolerate the vehicle misalignment specs. Thus making the total # of contactors to n×l2, where n is # of connectivity channels and l is the grid's linear dimension, which has to be bigger than vehicle parking tolerance in one dimension.
U.S. Pat. No. 5,651,434 has two overhead cables and the vehicle has a pantograph with two contactors insulated from each other. Due to the one to one correspondence between the infrastructure side and vehicle side contactors, this arrangement necessitates the two cables as well as the two pantograph connectors be separated laterally by the worst case lateral misalignment specs of the vehicle plus the lateral dimension of the pantograph contactors, making it a bulky system, which is difficult to extend beyond two connectivity channels, a prime safety requirement from ground fault detection viewpoint. U.S. Pat. No. 5,523,666 has features similar to contactor array structures; however it still depends on the mating pair of contactors to be brought together by active positioning. Again the one to one correspondence between the infrastructure and vehicle side connectors means relatively precise alignment at least in one direction, between the corresponding connectors is required. This alignment in the U.S. Pat. No. 5,523,666 is made by active positioning of the infrastructure rails and suffers from the consequent disadvantages of an active positioning system.
U.S. Pat. No. 5,252,078 is very similar to U.S. Pat. No. 5,523,666, except the relatively positioning of the mating connectors is achieved by passive compliant members. Both U.S. Pat. No. 5,252,078 and U.S. Pat. No. 5,523,666 suffer from the disadvantages of a system requiring precise alignment—whether passive or active, as well as carry potential for damage and reduced reliability and safety due to drivers accidentally driving into the system.
U.S. Pat. No. 4,158,802 is an overhead contactor system with one to one contactor correspondence between vehicle and infrastructure. Consequently suffers from either precise positioning or too large contactor spacing and size. As described, this system is also bulky and needs involved installation.
U.S. Pat. No. 4,850,879 is a front bumper variation of U.S. Pat. No. 6,307,347. Both, U.S. Pat. No. 4,850,879 as well as U.S. Pat. No. 6,307,347 describe conductor arrays that have contiguous domains of conductors that are electrically connected to each other and represent one single large conductor. Corresponding to one conductor (or a group of conductors that are electrically connected to each other) on ground, there is one and only one conductor on the vehicle that the ground conductor is permitted to pair with. All inventions based on one to one conductor pairing necessitate large individual conductors (or group of conductors) or accurate positioning. In case of U.S. Pat. No. 4,850,879, former is true. Additionally, U.S. Pat. No. 4,850,879 can be damaged due to accidental driving in.